Need help calculating this magnesium supplement

[john.m.cole3]

Let me tell you a little bit about my system first. 80 gallons is my total water volume comma I keep the temperature at 78 - 79.
Alk 9.6
Calc 490
Mag 1290 (up from 1230 on Saturday)
No3 10
Po4 .073
Mostly STony corals. 3 colonies, 30 frags.
Weekly 10% water change with aquaforest Reef salt.

Okay here's the reason for my post. I want to get my magnesium up to 1440 and the directions on the seachem bottle aren't exactly clear to me. Can Randy or somebody else help me out?

I used the last of my can't check in to get my levels from 1230 up to 1290. This stuff is all my lfs have left. Thank you

 

[Randy Holmes-Farley]

use the calculator entry for magnesium sulfate heptahydrate (Epsom salt) and multiple the amount of solid needed by 1.23. :)

http://reef.diesyst.com/chemcalc/chem_calc3.html